Automated blood cell analysis is a routine function in the clinical hematology laboratory. We have all had samples taken for such a purpose, but very few realize that the flow cytometric instrumentation performing these tests may have fundamental limitations regarding measurement of red blood cell volume, red blood cell hemoglobin concentration, and accurate classification of white blood cell subpopulations. 'High-end' instruments have become very complex and expensive in order to 'ensure' that an accurate and reliable result can be reported. There remains a gap in the availability of a low cost, easy to use system which can provide accurate and reliable cell data. This proposal describes two novel techniques applicable in clinical flow cytometry for hematologic analysis. Problems commonly associated with hemoglobin concentration measurements and cell volume interferences when making red blood cell measurements and problems of reproducibility of light scattering and volume interferences in the white blood cell differential measurement can be avoided. This is done by a new biomedical instrument that determines cell dry mass by measurements of phase shift using a two-frequency HeNe laser and cell volume by the principle of dye exclusion. The ultimate instrument will provide a unique capability as a low cost device for making accurate red and white blood cell dry mass and volume measurements in single cell analysis.